The rotation curves of disk galaxies exhibit a number of striking regularities. The amplitude of the rotation is correlated with luminosity (Tully-Fisher), the shape of the rotation curve is well predicted by the luminous mass distribution, and the magnitude of the mass discrepancy increases systematically with decreasing centripetal acceleration. These properties indicate a tight connection be...

Context. We present the results from a detailed X–ray variability analysis of 66 AGN in the Lockman Hole, which have optical spectroscopic identifications. Aims. We compare, quantitatively, their variability properties with the properties of local AGN, and we study the “variability – luminosity” relation as a function of redshift, and the “variability – redshift” relation in two luminosity

From the Press-Schechter mass function and the empirical X-ray cluster luminositytemperature (L-T ) relation, we construct an X-ray cluster luminosity function that can be applied to the growing number of high-redshift, X-ray cluster luminosity catalogs to constrain cosmological parameters. In this paper, we apply this luminosity function to the Einstein Medium Sensitivity Survey (EMSS) and the...

An empirical relation between the broad line region (BLR) size and optical continuum luminosity is often adopted to estimate the BLR size and then the black hole mass of AGNs. However, optical luminosity may not be a good indicator of photoionizing luminosity for extremely radio-loud AGNs because the jets usually contribute significantly to the optical continuum. Therefore, the black hole masse...

A new Monte-Carlo radiative-transfer code, Sunrise, is used to study the effects of dust in N-body/hydrodynamic simulations of interacting galaxies. Dust has a profound effect on the appearance of the simulated galaxies. At peak luminosities, ∼ 90% of the bolometric luminosity is absorbed, and the dust obscuration scales with luminosity in such a way that the brightness at UV/visual wavelengths...

In this paper we present a new, essentially empirical, model for the relation between the mass of a dark matter halo/subhalo and the luminosity of a galaxy hosted in it. To estimate this, we replace the assumption of linearity between light and mass fluctuations with the assumption of monotonicity between galaxy light and halo or subhalo mass. We are enabled to proceed with this less restrictiv...

The time-delay between the emission-line variations and the continuum variations of a quasar or Seyfert galaxy can be used to estimate the distance between the broad line regions (BLRs) and the central source, and this technique is called the emission-line reverberation mapping (RM). Based on the RM observation, a relationship between the size of BLRs (RBLR) and the luminosity of AGNs can be es...